Slit blade polishing procedure

ABSTRACT

A procedure for polishing slit blades to ensure proper flatness and blade angle. This task is incredibly difficult. The number of strokes, series of and type of abrasive papers used, direction of polishing lapping strokes, as well as other practices to promote flatness and minimize human and manufacturing error in the final slit blade product have all been experimentally determined by ADC personnel over years of experience and study. A fixture for holding blades while polishing the blade angle side has been developed to accommodate precise blade angle polishing.

CROSS REFERENCE TO RELATED APPLICATIONS

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STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

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SEQUENCE LISTING OR PROGRAM

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BACKGROUND OF THE INVENTION

In synchrotron research using x-rays, the x-ray beam size and shape isdefined by a device called a slit. The slit defines an aperture throughwhich the x-rays may pass through, by using blades made of materialsthat will absorb x-rays.

The blades are typically attached to actuators that can change the shapeof the aperture via computerized command to the actuator motors. Theseslit blades require the highest precision in terms of flatness and bladeangle.

By creating a polishing process to redefine flatness and blade anglelost due to use, new blades can be re-used. This is a cost effective wayto maintain apertures requiring slits.

SUMMARY OF THE INVENTION

The device described herein is a slit blade polishing proceduredeveloped to maximize the precision of blade flatness and blade angle.

Slit blades need to have a smooth matte finish and a sharp, defect freeknife edge in order to achieve the best possible focus of the beampassing through the aperture.

The process involves the use of several different sized grit paper,including silicon carbide paper and poly-crystalline diamond suspensionson fabric, application of pressure, compressed air, and a final polishwith colloidal silica.

The benefits of the implementation of such a process include substantialcost savings due to the ability to re-use slit blades after polishing,as opposed to total replacement, and maximization of precision of slitblade flatness and angle to provide the most accurate beam focus.

BRIEF DESCRIPTION OF DRAWINGS

The invention as described herein with references to subsequentdrawings, contains similar reference characters intended to designatelike elements throughout the depictions and several views of thedepictions. It is understood that in some cases, various aspects andviews of the invention may be exaggerated or blown up (enlarged) inorder to facilitate a common understanding of the invention and itsassociated parts.

FIG. 1 shows a schematic representation of a slit as used in thesynchrotron industry.

FIG. 2 shows an internal schematic representation of a slit used in thesynchrotron industry.

FIG. 3 shows the beam side of the slit blade.

FIG. 4 shows the backside of the slit blade.

FIG. 5 shows a side view of the slit blade.

FIG. 6 shows the parallel direction of lap strokes during the polishingprocedure as well as alternated direction between grit paper sizes.

DETAILED DESCRIPTION OF INVENTION

Provided herein is a detailed description of one embodiment of theinvention. Therefore, specific details enclosed herein are not to beinterpreted as limiting, but rather as a basis for the claims and as arepresentative basis for teaching one skilled in the art to employ thepresent invention in virtually any appropriately detailed system,structure, or manner.

The slit blade polishing technique in place at ADC consists of astep-by-step procedure in which slit blades of varying sizes and shapesare polished and finished in order to perform optimally.

FIG. 1 shows a schematic representation of a slit used in thesynchrotron industry. Within this schematic representation are theblades 7 in which the polishing procedure explained herein isimplemented upon. The aperture 8, or opening, is also shown. The openingdiameter and shape is changed using several slit blades. The accuracy towhich the diameter and shape of the aperture can perform is highlydependent upon the polishing and finishing of the slit blades. Slitblade widths vary from 10 to 35 mm and thickness of 1.5 to 12 mm. Bladesused in ADCs slit assemblies are made from either Tungsten or Tantalum.Blades 7 and aperture 8 of the overall slit is also shown in FIG. 2.This figure simply shows the internal schematic representation in orderto show location of slit blades within the slit, more accurately.

FIGS. 3, 4 and 5 show different views of one type, size and shape, ofslit blade in which this polishing procedure would be performed on.Specifically, FIG. 3 shows the beam side 9 of the slit blade, removedfrom the slit apparatus with the angle side 10 of the slit and 2° angleedge 11 of the slit blade. FIG. 4 is a view of the back side 12 of theslit blade with reference to the angle side 10 and 2° angle edge 11 ofthe slit blade. FIG. 5 is a side view of the slit blade, betterdemonstrating the angle side 10 and 2° angle edge 11; with view of thebeam side 9 of the blade.

The following contains the step by step procedure of the slit bladepolishing process with reference to slit blade components representednumerically as explained previously.

The beam side 9 is polished using progressively decreasing paper gritsize, demonstrated as follows: 180, 240, 320, and then 400 grit size.During this step, downward pressure is applied to the blade centerduring lapping; one lap is equivalent to a forward and backward strokeacross the blade. Five to eight lap strokes are completed for each papergrit size, demonstrated in FIG. 6.

Staring with the first grit, 180, lapping is done left to right, orright to left. For each progressive grit paper, lapping direction isalternated to promote flatness, compensating to a degree, for what isknown as human error, also demonstrated in FIG. 6. Lap strokes are doneparallel to the knife edge with incremental moves sideways as lappingprogresses, keeping the knife edge trailing in order to retain bladeflatness. Once this is completed, the blade is blown off with compressedair to remove any remaining material removed during polishing.

Next, the attention is moved to the 2° angle side 10 of the slit blade.This side is not the critical side to be polished in this process,however, the polishing of this side aides in the sharpness of the edge11 created between the beam side 9, where the incident beam actuallystrikes when blades are within the slit apparatus, and angle side 10,which increases sharpness and accuracy of the beam created as it passesthrough the opening 8 created by several different slit blades withinthe complete device.

The angle fixture is placed on 0.002″ stainless steel shims and clampedin with one to four blades, depending on how many are used for thesystem. This is done to maintain parallelism. A backing plate is usedbetween the back side of the blades and the swivel head set screws inorder to prevent bending of the blades during polishing. If multipleblades are clamped together during this process, the blades are to beprotruding evenly, ˜0.002″ from the bottom of the fixture.

The angle side 10 of the blades are then polished identical to the beamside 9 of the blade, using progressively decreasing paper grit size,demonstrated as follows: 180, 240, 320, 400, 600, 800 then 1200. Duringthis step, downward pressure is applied during lapping; one lap isequivalent to a forward and backward stroke across the blades angleside. Five to eight lap strokes are completed for each paper grit size.Lap strokes are done parallel to the knife edge with incremental movessideways as lapping progresses, keeping the knife edge trailing in orderto retain blade flatness, demonstrated in FIG. 6.

Starting with 180 grit paper, lapping is done left to right, or right toleft. For each progressive grit paper, lapping direction is alternatedto promote flatness, compensating to a degree, for what is known ashuman error. Final polishing of the blade angle side 10 is done using1200 grit silicon carbide paste on a tungsten lapping plate. After this,attention is returned to the beam side of the slit blade.

The beam side 9 is polished using progressively decreasing paper gritsize, demonstrated as follows: 600, 800 and then 1200. After this, theslit is blown off with compressed air in order to remove any remainingmaterial, removed during the polishing process. Starting with 600 gritpaper, lapping is done left to right, or right to left. For eachprogressive grit paper, lapping direction is alternated to promoteflatness, compensating to a degree, for what is known as human error.Final polishing of the blade beam side 9 is done using 1200 grit siliconcarbide paste on a tungsten lapping plate, after which, is reviewedunder a microscope, checking for a flat and matte finish with a defectfree knife edge.

During the entire polishing process, it is essential that there are noair bubbles beneath the grit paper, and that blades are blown off withcompressed air between each grit type.

At the end of any grit phase, flatness can be checked by applying waterand observing the water bead formed. If the polished surface is flat,the surface tension of the water will cause it to bead from edge toedge. If the polished surface is waned off, decreasing in flatness orslightly rounded downward or upward, the water will stop at thebeginning of the angle change. When it is apparent that the bladespolished surface is not flat, the blade is re-flattened, starting with320 grit paper, and following the successive steps as listed above.

What is claimed is:
 1. A methodical procedure for polishing slit bladesfor x-ray beam size definition.
 2. The method of claim 1 wherein thestep-by-step procedure listed is used for slit blades of varying sizes,ranging from: (a) 10 to 35 mm in width and (b) 1.5 to 12 mm inthickness.
 3. The apparatus of claim 2 wherein said slit blades are madeof either: (c) Tungsten or (d) Tantalum.
 4. The method of claim 2wherein said step-by-step procedure begins with polishing the beam sideof the apparatus of claim 2 using: (e) 180 grit paper (f) a lappingtechnique, one forward and one back stroke across the blade, five toeight lap strokes and (g) blowing said slit blade with compressed air 5.The method of claim 4 wherein continuation of said step-by-stepprocedure occurs, using 240 grit paper and following steps (f) and (g)of method of claim
 4. 6. The method of claim 4 wherein continuation ofsaid step-by-step procedure occurs, using 320 grit paper and followingsteps (f) and (g) of method of claim
 4. 7. The method of claim 4 whereincontinuation of said step-by-step procedure occurs, using 400 grit paperand following steps (f) and (g) of method of claim
 4. 8. The method ofclaim 1 wherein polishing continues on the 2° angle side of the slitblade, wherein said blade angle fixture is placed on 0.002″ stainlesssteel shims and clamped in with one to four blades, depending per thesystem, to maintain parallelism while polishing.
 9. The method of claim8 wherein the step-by-step procedure of claim 2 is carried out beginningwith 180 grit paper and following steps (f) and (g) of method of claim4.
 10. The method of claim 8 wherein the step-by-step procedure of claim2 is carried out beginning with 240 grit paper and following steps (f)and (g) of method of claim
 4. 11. The method of claim 8 wherein thestep-by-step procedure of claim 2 is carried out beginning with 320 gritpaper and following steps (f) and (g) of method of claim
 4. 12. Themethod of claim 8 wherein the step-by-step procedure of claim 2 iscarried out beginning with 400 grit paper and following steps (f) and(g) of method of claim
 4. 13. The method of claim 8 wherein thestep-by-step procedure of claim 2 is carried out beginning with 600 gritpaper and following steps (f) and (g) of method of claim
 4. 14. Themethod of claim 8 wherein the step-by-step procedure of claim 2 iscarried out beginning with 800 grit paper and following steps (f) and(g) of method of claim
 4. 15. The method of claim 8 wherein thestep-by-step procedure of claim 2 is carried out beginning with 1200grit paper and following steps (f) and (g) of method of claim
 4. 16. Themethod of claim 1 wherein final polishing of the blade angle side isdone using 1200 grit silicon carbide paste on a tungsten lapping plate.17. The continuation of the method of claim 7 wherein beam sidepolishing is continued using 600, 800 then 1200 grit paper to completethe polishing of said slit beam side.
 18. The method of claim 7 whereinfinal beam side polishing is done using 1200 grit silicon carbide pasteon a tungsten lapping plate.
 19. A checking procedure wherein flatnesscan be checked throughout the polishing method of claim 1 by applyingwater to the slit blade and observing movement of beading. When waterbeads from edge to edge, flatness has been achieved. If said waterceases movement at any point, flatness no present.
 20. The method ofclaim 19 wherein the event that flatness has not been achieved, bladesurface is to be re-flattened beginning with method of claim 6 andcontinuing to the method of claim 18.